1. Field of the Invention
This invention relates generally to an endoscope, and more particularly an endoscope incorporating a device for bending a bendable portion of the endoscope.
2. Prior Art
Generally, an endoscope includes a body, an insertion portion extending from the body, and a bendable portion extending from a forward end of the insertion portion. Devices for bending such a bendable portion are disclosed in U.S. Pat. Nos. 4,718,407, 4,721,099 and 4,834,069, and such a device includes one or two pairs of operating wires. These operating wires are passed through the insertion portion and the bendable portion, and are connected at their distal ends to the distal end of the bendable portion in spaced relation to each other. The proximal end portions of the operating wires are received in the body of the endoscope. One or two operating shafts are mounted on the body, and a manipulating member is mounted on one end of the operating shaft, extending exteriorly of the body, so as to angularly move the operating shaft. A pulley is fixedly mounted on the operating shaft, and each pair of operating wires are fixedly connected at their proximal ends to the peripheral surface of the pulley. When the operating shaft is angularly moved, one of the pair of operating wires associated therewith is pulled, so that the bendable portion is bent or flexed.
Among the users, there has now been a demand that the bendable portion can be bent to a large extent with a small amount of angular movement of the manipulating member in order to rapidly bend the bendable portion to a desired extent. However, the devices for bending the bendable portion of the endoscope, as disclosed in the above-mentioned U. S. patents, have failed to meet this demand. The reason for this will now be described. The amount of bending of the bendable portion is determined by the amount of movement of the proximal ends of the pulled operating wire, and this amount of movement is equal to the amount of angular movement of the outer periphery of the pulley. Therefore, in order to meet the above demand, it is necessary to increase the diameter of the pulley, and this results in an increased size of the body. However, the increase in size of the body is limited, because with the increase in the body size, the operator is susceptible to fatigue when operating the bendable device.
In such a construction as disclosed in the above-mentioned U.S. patents, in which the bendable portion can be bent by pulling a selected one of the operating wires, there is a possibility that the bendable portion may be bent in a twisted manner. The reason for this is that an optical fiber bundle, tubes and other elements which are different in rigidity are received asymmetrically in the bendable portion, so that these component parts offer uneven resistances to the bendable portion when the bendable portion is being bent. To overcome this difficulty, Japanese Laid-Open (Kokai) Patent Application No. 121532/81 has proposed a bending device in which two out of four operating wires are to be pulled simultaneously. More specifically, the first, second, third and fourth operating wires are fixedly connected at their distal ends to the distal end of the bendable portion in such a manner that these fixed distal ends of the four operating wires are disposed in this order on a circle, lying in a plane perpendicular to the axis of the bendable portion, and are circumferentially spaced from one another. Connecting members are connected to the proximal ends of the operating wires, respectively, and each connecting member has a pair of first and second holes formed therethrough. A pair of pulleys are fixedly mounted on each of two operating shafts, and a pair of driving wires are fixedly connected at their one ends to the diametrically opposite portions of the outer peripheral surface of each of the pulleys, respectively, and extend from the pulley toward the bendable portion. The four driving wires operable by one of the operating shafts are passed respectively through the first holes in the four connecting members whereas the other four driving wires operable by the other operating shaft are passed respectively through the second holes in the four connecting members. A stop member is fixedly connected to the other end of each of the driving wires.
In this conventional device of the above Japanese Laid-Open Patent Application No. 121532/81, the following function is intended. When one of the operating shafts is angularly moved together with the pair of pulleys mounted thereon, the first and second operating wires or the third and fourth operating wires are pulled simultaneously through two of the driving wires connected to these pulleys and also through two of the connecting members with which the stop members, mounted respectively on these two driving wires, are engaged. As a result, the bendable portion is bent upwardly or downwardly. On the other hand, when the other operating shaft is angularly moved, the second and third operating wires or the first and fourth operating wires are pulled simultaneously to bend the bendable portion in a left-hand direction or in a right-hand direction.
In this conventional device, when the bendable portion is not in its bent condition, the stop members abut against the end faces of the connecting members, respectively, and therefore actually the bendable portion can not be bent as desired. More specifically, when one of the operating shafts is angularly moved together with the two pulleys mounted thereon, so as to pull, for example, the two driving wires connected respectively to the lower sides of these two pulleys, the two connecting members, with which the stop members on these two driving wires are engaged, try to move away from the bendable portion to pull the two operating wires, connected to these two connective members, so as to bend the bendable portion, for example, downwardly. At this time, although the other two operating wires connected respectively to the other two connecting members are pulled by the bendable portion, these two operating wires can not be moved toward the bendable portion. The reason is that these two connecting members are prevented from movement by the stop members connected to those driving wires operatively associated with the other operating shaft remaining stationary. As a result, the bendable portion is prevented from being bent.
As is clear from the foregoing, in the device of the above-mentioned Japanese Laid-Open Patent Application No. 121532/81, when the bendable portion is to be bent, it is necessary that all the stop members connected respectively to the driving wires be spaced apart from their mating connecting members, respectively, while maintaining the bendable portion in a straight condition. However, when such spacing or play is provided, the operating wires can not be pulled at an initial stage of the angular movement of the operating shaft, so that the bendable portion can not be bent at this initial stage, thus adversely affecting the operability.